On Fri, 27 Sep 2019 16:25:13 +0000
Parav Pandit <parav@xxxxxxxxxxxx> wrote:
> Hi Alex,
>
>
> > -----Original Message-----
> > From: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > Sent: Tuesday, September 24, 2019 6:07 PM
> > To: Jason Wang <jasowang@xxxxxxxxxx>
> > Cc: kvm@xxxxxxxxxxxxxxx; linux-s390@xxxxxxxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; intel-
> > gfx@xxxxxxxxxxxxxxxxxxxxx; intel-gvt-dev@xxxxxxxxxxxxxxxxxxxxx;
> > kwankhede@xxxxxxxxxx; mst@xxxxxxxxxx; tiwei.bie@xxxxxxxxx;
> > virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx;
> > cohuck@xxxxxxxxxx; maxime.coquelin@xxxxxxxxxx;
> > cunming.liang@xxxxxxxxx; zhihong.wang@xxxxxxxxx;
> > rob.miller@xxxxxxxxxxxx; xiao.w.wang@xxxxxxxxx;
> > haotian.wang@xxxxxxxxxx; zhenyuw@xxxxxxxxxxxxxxx; zhi.a.wang@xxxxxxxxx;
> > jani.nikula@xxxxxxxxxxxxxxx; joonas.lahtinen@xxxxxxxxxxxxxxx;
> > rodrigo.vivi@xxxxxxxxx; airlied@xxxxxxxx; daniel@xxxxxxxx;
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> > lingshan.zhu@xxxxxxxxx; Ido Shamay <idos@xxxxxxxxxxxx>;
> > eperezma@xxxxxxxxxx; lulu@xxxxxxxxxx; Parav Pandit
> > <parav@xxxxxxxxxxxx>; christophe.de.dinechin@xxxxxxxxx;
> > kevin.tian@xxxxxxxxx
> > Subject: Re: [PATCH V2 6/8] mdev: introduce virtio device and its device ops
> >
> > On Tue, 24 Sep 2019 21:53:30 +0800
> > Jason Wang <jasowang@xxxxxxxxxx> wrote:
> >
> > > This patch implements basic support for mdev driver that supports
> > > virtio transport for kernel virtio driver.
> > >
> > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > ---
> > > include/linux/mdev.h | 2 +
> > > include/linux/virtio_mdev.h | 145
> > > ++++++++++++++++++++++++++++++++++++
> > > 2 files changed, 147 insertions(+)
> > > create mode 100644 include/linux/virtio_mdev.h
> > >
> > > diff --git a/include/linux/mdev.h b/include/linux/mdev.h index
> > > 3414307311f1..73ac27b3b868 100644
> > > --- a/include/linux/mdev.h
> > > +++ b/include/linux/mdev.h
> > > @@ -126,6 +126,8 @@ struct mdev_device *mdev_from_dev(struct device
> > > *dev);
> > >
> > > enum {
> > > MDEV_ID_VFIO = 1,
> > > + MDEV_ID_VIRTIO = 2,
> > > + MDEV_ID_VHOST = 3,
> >
> > MDEV_ID_VHOST isn't used yet here. Also, given the strong interdependence
> > between the class_id and the ops structure, we might wand to define them in
> > the same place. Thanks,
> >
>
> When mlx5_core creates mdevs (parent->ops->create() and it wants to
> bind to mlx5 mdev driver (which does mdev_register_driver()), mlx5
> core driver will publish MDEV_ID_MLX5_NET defined in central place as
> include/linux/mdev.h without any ops structure. Because such ops are
> not relevant. It uses usual, standard ops probe() remove() on the
> mdev (similar to a regular PCI device). So for VHOST case ops may be
> closely related to ID, but not for other type of ID.
>
> Just want to make sure, that scope of ID covers this case.
AIUI, these device-ops are primarily meant to have 1:N multiplexing of
the mdev bus driver. One mdev bus driver supports N vendor drivers via
a common "protocol" defined by this structure. vfio-mdev supports
GVT-g, GRID, and several sample drivers. I think Jason and Tiwei are
attempting something similar if we have multiple vendors that may
provide virtio/vhost parent drivers. If you have a 1:1 model with
mlx5 where you're not trying to abstract a common channel between the
mdev bus driver and the mdev vendor driver, then I suppose you might
not use the device-ops capabilities of the mdev-core. Did I interpret
the question correctly? I think that's probably fine, mdev-core
shouldn't have any dependencies on the device-ops and we shouldn't
really be dictating the bus/vendor link through mdev. Thanks,
Alex
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